Live From Mars was active July 1996-December 1997.


Things are Hectic!

by Greg Wilson

February 20, 1997

Sorry for not keeping my journal up to date, but things have been busy around here lately. I remember talking a lot about writing proposals in my first journal, and now I am happy (Ecstatic!) to report that my proposal to do atmospheric science on Mars Pathfinder was accepted. And to top it all off, a second proposal submitted last April was accepted right after the Christmas holidays. So now I am pretty busy just keeping everything going.

The Mars Pathfinder (MPF) team is great. You can examine our abstracts on the MPF Web page ( We have already planned measurements for the first seven sols (Martian days) and are really excited about some of the new measurements we will be making. It is also a great privilege to work with some of the most knowledgeable Mars atmospheric scientists in the world, and especially Al Seiff, who has measured the upper atmosphere of every planet we have sent spacecraft to (Venus, Earth, Mars and Jupiter, and in the future Titan!).

Our excitement is tempered by some problems we have to overcome. The offset on the pressure sensor has changed since its initial calibration. An offset is a number that you add or subtract from your instrument measurement before you convert it into pressure (this number is also a function of instrument temperature). So what we have been doing during the cruise phase of the mission is to measure the offset periodically.

These measurements are called health checks (HC), and nine of them have been performed during the mission thus far. Two weeks ago, while down at the Jet Propulsion Laboratory (JPL), I had the chance to participate in HC#8. It was really pretty cool. The command was sent to the spacecraft to perform the HC, and two minutes later (equal to the round-trip light time) data started appearing on the computer console in front of me. We also got a three-day briefing on the spacecraft and all of its subsystems. I can't say enough about the MPF flight team at JPL, they are super!

Back at the Planetary Aeolian Laboratory things are hectic. Wind tunnel experiments of Martian dust threshold are continuing. I will be traveling to Houston, TX next month to present two posters and give a talk on the research results of the past year (all of which I have yet to prepare!).

My new proposal, just funded with Dr. Bruce White, will be looking at atmospheric stability effects on particle threshold under Martian conditions. When the sun heats up the surface of Mars, the atmosphere near the surface heats up and rises; we call this condition unstable. These rising parcels of atmosphere add some additional shear energy to the wind. We have previously only considered wind shear (neutral) and neglected the additional shear when looking at particle threshold, but what we think will happen when we include this effect is that it should take less wind shear to move the particles. The contrary should also be true (stable). If upper the upper-level atmosphere is cooler, the parcels will fall, dampening the shear stress and increase the wind shear need to move the particles. So the results of this experiments should be pretty cool.

Finally, we are in the first stages of testing the two wind sensors on the Mars 98 mission. Dr. David Crisp, Colin Mahoney, and Rudy Vargas, all from JPL, have been at the Mars Wind Tunnel twice during the past two months to test the "proof of concept" wind sensors. Things look pretty good so far. The sensor is using a lot less power then the MPF wind sensor, and can measure winds up to 95 meters per second (that's about 200 miles per hour)! So that has been a lot of fun. I really enjoy the interaction I have with the scientists and engineers. Whenever you do an instrument test there is a "middle- ground" where theory (science) and application (engineering) meet. After putting in a few long days together, you can really appreciate the contribution each person makes to the team.

On the personal side things are going pretty well. Now that the weather is better I have been flying my radio-controlled plane on the weekends or at least until it crashes! My girlfriend and I are hoping to do some whale watching in the next couple of weeks. I have not taken much time off since summer vacation, and am hopeful of taking some time off before July, when I will participate in the MPF prime mission. More on that in my next journal.